Viscose rayon fiber and method of making same



Oct. 4, 1966 G. c. BOCKNO ETAL 3,277,226

VISCOSE RAYON FIBER AND METHOD OF MAKING SAME Filed'April 9, 1962 United States Patent 3,277,226 VISCOSE RAYON FIBER AND METHOD OF MAKING SAME Gregory C. Bockno, Media, and Anthony P. Da Vinci, Trainer, Pa., assignors, by mesne assignments, to FMC Corporation, San Jose, Calif., a corporation of Dela- Ware Filed Apr. 9, 1962, Ser. No. 185,936 7 Claims. (Cl. 264198) This invention relates to synthetic fibers, more particularly to a new and novel regenerated cellulose or viscose rayon fiber, to a process for producing such fiber and fabrics containing the fiber.

While many forms of regenerated cellulose fibers have been produced and they have attained widespread use and acceptance because of their strength, luster, softness and hand, they have had certain physical characteristics that have limited their use in some fields in place of cotton or in blends with cotton. Desirable properties of cotton fiber .are its high elastic modulus and low extensibility when wet or conditioned and the relatively reduced shrinkage of fabrics when wet and then dried. Regenerated cellulose fibers of the prior art that were not too brittle or did not fi-brillate were characterized by excessive shrinkage when wet and then dried and a relatively low elastic modulus both wet and conditioned. Fabric woven of the prior art regenerated cellulose could not be stabilized by physical stabilizing processes but required relatively expensive chemical or resin treatment for this purpose.

Regenerated cellulose or viscose rayon fibers are, in effect, tailor-made for specific end uses. The specific end use determines the method employed in producing the fibers and the specific composition of the viscose solution and the spinning bath or baths and the specific conditions employed in the methods of production. Slight changes in the composition of the viscose and spinning baths and slight alterations in the methods of production result in fibers having an extremely wide range of properties. In general, in the production of viscose rayon fibers having a high Wet modulus, it has been necessary to utilize viscose solutions having a low cellulose content and spinning the filaments at a very low speed.

One of the principal objects of the present invention is to provide viscose rayon fibers having high strength characteristics and a high wet modulus without being excessively brittle or fibrillatable.

A further object of the invention is to provide viscose rayon fibers having a high wet modulus and a low water pick-up and low shrinkage characteristics.

Another object of the invention is to provide viscose rayon fibers having a high wet and conditioned modulus and high wet and dry or conditioned strengths.

Still another object is to provide a method of forming fibers of the foregoing characteristics at .a reasonably high spinning speed.

A further object of the invention is to provide a woven fabric containing viscose rayon fibers that may be stabilized against excessive shrinkage by physically compressing the fabric in the direction of its warp.

Other objects and advantages of the invention will become apparent from the following description and claims.

The drawing is a diagrammatic illustration of apparatus for the production of the fibers and for the practice of the present invention.

The present invention contemplates the production of a high strength, high wet modulus viscose rayon fiber at a commercially feasible rate of speed by utilizing 3,277,226 Patented Oct. 4, 1966 viscose and a spinning bath both having composition ranges within rather narrow limits, and spinning the viscose under a limited range of conditions.

The invention is applicable to the production of continuous filaments or staple fibers in a wide range of deniers, for example, the denier may be from 1.0 to 3.0 or greater in accordance with conventional practice relating to viscose rayon filaments and yarns. It is well known that in the production of synthetic staple fibers, the viscose is converted into a continuous filament and the staple fibers are produced by cutting the continuous filaments to a desired length. In the discussion which follows, the term fiber will be used, and it is to be understood that this term is being used to designate both continuous filament and staple fiber.

One of the unique characteristics of the present fiber is its high tenacity or tensile strength in both the wet and dry or conditioned state. The tenacity in the wet state is at least about 3.0 grams per denier. In the conditioned state, that is, after the fiber has been initially dried and then allowed to remain in an atmosphere having a relative humidity of 58% and a temperature of F. for twenty-four hours, the fiber has a tenacity of at least 4.7 grams per denier. In general, the wet tenacity will vary from about 3.0 to about 3.5 grams per denier and the conditioned tenacity will vary from about 4.7 to about 5.5 grams per denier. Another particularly unique characteristic of the present fiber is that it resembles cotton very closely in its wet modulus, shrinkage characteristics and ultimate extensibility or elongation in both the wet and conditioned states. Because of these characteristics, the fiber may replace cotton for many textile purposes or may be blended with cotton. It also possesses the desirable characteristics of other viscose rayon textile fibers with respect to luster, softness and hand. Fabrics formed of the fiber may be stabilized by physically compressing the fabric .in a warpwise direction by Well known methods such as the process associated with the trademark Sanforize as disclosed in the patent to Cluett 1,861,422, May 31, 1932.

One of the factors which has greatly limited the blending of textile grades of rayon fibers with cotton has been the appreciable loss, about 30% in strength of rayon fibers when subjected to the usual caustic soda treatment in mercerizing of cotton yarns and fabrics. Because of this appreciable loss in strength and the difficulties encountered in attempting to impart dimensional stability to rayon fibers and fabrics, the rayon content of blends of cotton and the prior are rayon fibers has been stricted to a maximum of about 30%. The fiber of this invention, on the other hand, when subjected to a mercerization treatment results in a loss of tensile strength of only 10% In view of the initial high tenacity or tensile strength of the present fiber, such loss in strengthdoes not seriously affect the strength of the cotton blend yarns and fabrics. Furthermore, the ability to stabilize dimensionally the fabrics formed of this fiber by physical treatment of the fabric permits the use of blends of cotton and this new fiber wherein the rayon content may be from 10% or less to about 70% to 75%.

The wet modulus as used herein is an average wet modulus and is the amount of stress in grams per denier of the fiber required to stretch the fully wet fiber 5% of its length divided by 0.05 which is the strain. The extensibility or elongation is the amount of stretching generally reported in percentage of the fiber length at the point of breaking of the fiber. Measurements of wet modulus and elongation or extensibility may be made on the conventional Instr-on Tensile Tester by conventional procedure. The wet modulus of the viscose rayon fiber of the present invention varies between about 12 and 20.

This characteristic is just slightly less than the corresponding characteristic of cotton fibers and, hence, the fiber stretches to about the same extent as cotton during Weaving and finishing of a woven fabric. This characteristic also contributes to the ability of increasing the rayon content of blends of cotton and rayon to 70% to 75%. This factor is a measure of the resistance of the fiber to stretching or elongation when subjected to tension. The elongation or extensibility of the fiber is generally Within the range of from 15% to 22% when wet and about 12% to 15% in the conditioned state.

Woven fabrics formed entirely of these viscose rayon fibers have a residual shrinkage or will shrink after successive washings about or less which is again about the same as untreated cotton fabrics. The residual shrinkage of a woven fabric can be reduced to about 2.2% by subjecting the fabric to a compression treatment in the direction of the warp as shown in the patent to Cluett 1,861,422. This degree of shrinkage is similar to the residual shrinkage for corresponding cotton fabrics. Fabrics formed of the fiber exhibit about the same wet warp tensile strength as those formed of cotton. However, they exhibit a warp tensile strength in a conditioned state of about 25% greater than corresponding cotton fabrics.

Prior rayon fibers having a high strength and a high wet modulus have been characterized in having an undesirable property of fibrillating excessively. A very distinctive attribute of the fibers of this invention is their low fibrillation which is about the same as that of conventional textile grade rayon.

Fibrillation is the splitting or peeling 01f of portions of the fiber. The portions or fibrils either break off entirely or peel part way from the periphery of the fiber much like a banana is peeled. The fibrillation reduces the size and strength of the fiber, it also makes the fiber appear fuzzy or frayed. Fabrics containing fibers that fibrillate readily and which are dyed appear to change to lighter shades in those areas containing such fiber because of the light-scattering effect of the fibrillated fibers. This is particularly noticeable in fabrics of the dark colors.

The amount of fibrillation of the fiber may be determined and measured by the filtering properties or Water fiow number of certain Weight of the fiber that has been beaten in a Waring type mixer or heater for a certain period of time. The Water flow number as used in this specification and in the claims hereof is determined by adding 4 grams of the fiber in 300 grams of water to a Waring type beater where it is beaten for 20 minutes. The fiber in the Water is screened by passing the slurry through an 80 mesh screen which removes the fibrils or particles that are broken off. The screened fiber and 180 grams of water are placed in a Battista HF thimble having a sintered glass filter plate therein. This thimble filter is a standard article of commerce made by the Ace Glass Company of Vineland, New Jersey, and is described in a technical article entitled Hydro Cellulose Water Flow Number by O. A. Battista, J. A. Howsmon and Sidney Coppick in Industrial and Engineering Chemistry, volume 45, page 2107, September 1953.

The sintered glass filter has an average pore size of 40 microns and is approximately one and one-quarter inches in diameter and one-sixteenth inch in thickness. The fiber when placed in the thimble with the water is allowed to settle and form a fiber pad on the filter disc. The pressure on the lower side of the filter disc is reduced by an amount equal to a pressure of 60 millimeters of mercury. The liquid is all-owed to flow through the fibrous pad and the sintered glass filter while this slight vacuum is maintained. The time required for 100 cubic centimeters of water to flow through the fiber pad and the sintered glass filter plate is measured in seconds. This number of seconds is the water flow number.

The fibers and filaments of this invention are obtained only by a close control and correlation of the viscose composition, the spinning bath composition and the spinning conditions. The viscose contains from 5% to 7% cellulose, from 5% to 10% caustic and from 30% to 38% carbon disulfide, based upon the weight of the cellulose. It is essential that the ratio of the proportions of the cellulose to the caustic soda be maintained within the range of 1:1 to about 121.4.

The viscose is formed in the conventional manner and either during its preparation or just prior to spinning is modified by the addition of a viscose or coagulation modifier. A large number of modifiers are known and are in use in the production of the various types of viscose rayon. These modifiers include polyoxyalkylene glycols such as polyoxyethylene glycols, polyoxypropylene glycols and block copolymers of propylene and ethylene oxides; tvarious amines including monoamines, diamines and polyamines such as diethylamine, dimethylamine, ethylene diamine and diethylenetriamine; reaction products of alkylene oxides with fatty acids, fatty alcohols, fatty amines, aromatic acids, aromatic alcohols, aromatic amines, partial esters of fatty acids and polyhydric alcohols such as reaction products of ethylene oxide with lauryl alcohol, phenol, lauryl amine, glycerol monostearate, etc.; quaternary ammonium compounds and the like.

The amount of modifier may vary from about 2% to about 5%, based on the weight of the cellulose.

For the purposes of the present invention, it is preferred to utilize a combination of modifiers such as a monoamine and a polyoxyalkylene glycol or a polyoxyalkylene glycol ether of an aromatic alcohol or a polyhydric alcohol wherein the glycol or ether has a molecular Weight of between about 600 and about 4000 to 6000; for example, dimethylamine and a polyoxyethylene glycol or a polyethylene glycol ether of phenol or sorbitol having a molecular Weight within the stated range. In the use of the combination, the monoamine is added in an amount of from about 1.5% to 3.5% and the glycol or ether in an amount of from about 1% to 3%, both proportions being based upon the weight of the cellulose.

The viscose is aged (including the mixing and holding periods) from 10 to 30 hours and has a total sulfur content of approximately 1.4% to 1.9% and a xanthate sulfur content of from about 1.0% to 1.4%. The sodium chloride salt test may be between 7 and 9 at the time of spinning and the ball fall is between 55 and 90.

The spinning bath may be classed as a low-acid, lowsalt bath and should contain between 6% and 9% sulfuric acid, 2.5% to 7% zinc sulfate and from 10% to 14% sodium sulfate. During spinning, the temperature of the bath should be maintained between 25 C. and 40 C. and the spinning speed may be between 20 and 40 meters per minute. From the spinning bath, the filaments prior to washing are passed through a second bath or stretch bath maintained at a temperature between C. and C. and the filaments are stretched from about to about during their travel through this bath. The stretch bath may be a hot water bath or may contain from 1% to 5% sulfuric acid, about 1% to ;l% zinc sulfate and from about 4% to 7% sodium sulate.

Filaments and fibers produced from the viscose and spun under the foregoing conditions possess the properties and characteristics as described herein.

The fibers and filaments may be produced and the method of forming them may be practiced in conventional equipment such as that shown diagrammatically in the accompanying drawing. A trough or tank 1 is provided as a container for the spinning bath 2 which is generally recirculated in practice. Means for circulating the bath are not shown, such means being conventional in the art. A spinneret 3 mounted at the end of rounder 4 is positioned in the tank 2 being submerged in the spinning bath. The viscose is delivered from a suitable source (not shown) to the rounder and is extruded through the spinneret to form the filaments 5 which upon leaving the spinning bath pass to positively driven godet 6 and then on to a second positively driven godet 7. The godet 7 -is driven at a speed greater than godet 6 and the relative speeds of the godets are selected so as to provide for the required stretching of the filaments between the two godets. Interposed between the godets, there is mounted a trough 8 through which a second or stretching bath is passed. The stretching bath is maintained at a high temperature which plasticizes to some extent the filaments and permits a higher degree of stretching. The stretching bath also effects a further regeneration of the cellulose in the coagulated and partially regenerated filaments formed in the spinning bath 2. From the godet 7, the filaments may be passed through suitable aftertreatment zones and then collected on a cone or in a conventional spinning box or bucket. Alternatively, the filaments may pass from godet 7 to a suitable cutting device wherein the filaments are cut to form the staple fibers of a desired length. Conventionally, the staple fibers are then deposited as a mat and the mat of fibers then subjected to the required aftertreatments.

To illustrate more specifically the method of forming filaments and fibers of the present invention, the following example is included.

EXAMPLE Viscose was prepared by treatment of pulp sheets (high alpha cellulose, viscose grade pulp) with caustic soda, shredding the resulting alkali cellulose, xanthating the alkali cellulose and dissolving it in a caustic sod-a solution. The viscose so prepared contained 6% cellulose, 7% caustic soda and 34% carbon disulfide based upon the weight of the cellulose. In this specific example, the cellulose to caustic soda ratio was 1.0 to 1.17. The viscose was then aged in the conventional manner at 18 C. for 12 hours. The viscose at the time of spinning had a sodium chloride salt test of 8.0, a ball fall viscosity of 60 to 75 seconds. The total sulfur content was 1.6% to 1.7% and the xanthate sulfur was 1.1% to 1.2%. 3.3% dimethylamine and 1.7% of a polyoxyethylene glycol ether of phenol containing an average of 15 ethylene oxide units per mole of phenol was incorporated in the viscose during the mixing operation. The dimethylamine and phenol ether may be added at any stage in the preparation of the viscose.

The viscose was spun to form a 1.5 denier, 12,000 filament yarn by extrusion of the viscose through orifices about 0.0025 in. in diameter into a spinning bath containing 7% sulfuric acid, 11% sodium sulfate and 4% zinc sulfate, the spinning bath being maintained at a temperature of about 30 C. The filaments were withdrawn from the bath, passed over a first godet, through a hot second bath, over a second godet and then collected and after-treated. The second bath was formed by diluting some of the spinning bath and contained about 3% sulfuric acid, about 1.5% zinc sulfate and about 5% sodium sulfate and was maintained at a temperature of about 95 C. During passage of the filaments through the hot bath, they were stretched approximately 140%. The spinning speed was about 25 meters per minute. After collecting the rfilaments, they were washed, desulfurized and bleached by conventional treatments.

The physical properties of the filaments are set forth in the following table:

Table 1 Strength, gms./denier:

Wet 3.40

Conditioned 5.00 Elongation, percent:

Wet 17 Conditioned 15 Cross Sectional Swelling, percent 45.1 Wet Modulus at 5% Elongation 15 Wet Stiffness Factor 20.0

6 Water Flow Number 9.85 Single Fiber Flex, cycles 115,000 Cross-Section Round Skin, percent 30 Fibrillation None The Wet Stiffness Factor is the wet strength in grams per denier divided by the percent elongation in a wet state.

The Single Fiber Flex is measured on a Fiber Flex Tester made by Fiber Test Inc., Arcweld Building, Grove City, Pennsylvania. This testing machine measures the resistance of single fibers to fatigue in flexure. In this apparatus, a fiber is secured to a reciprocating element and passes over a carefully machined bar having an edge closely ground to a diameter of approximately 0.005 inch and the other end of the filament is secured to a small weight. As the element is reciprocated, the filament is drawn across the edge of the bar. The number of cycles up to the time the filament breaks is recorded. As reported in the above table, 10 filaments were subjected to this test and the number of cycles is reported at the time the sixth of the ten fibers fail. This is considered the median value. The corresponding Single Fiber Flex Test for cotton showed 69,000 cycles. This test is directly related to the wear properties of fabrics formed of the specific fibers. This method of testing fibers is described in an article by Lefferdink and Briar Interpretation of Fiber Properties published in Textile Research Journal, volume 29, June 1969.

The fibrillation is measured by subjecting the fibers to the action of a Waring type beater for 20 minutes and examining fibers under the microscope.

Staple fibers as described in the foregoing example having a length of 1 and a... inch were spun to form a 30/ 1 yarn which was then woven into a standard '64 x 62 challis construction. Samples of the fabric were processed in the usual manner by singeing, desizing, scouring, bleaching and drying. Certain samples were subjected to a conventional Sanforizing treatment and other samples were subjected to a conventional resin treatment using a 5% solution of a urea-formaldehyde resin (dimethylol urea-Rhonite R 1, manufactured by Rohm & Haas Co., Philadelphia, Pennsylvania).

The plain finished fabric samples when subjected to 10 successive boiling washes in accordance with Test Method 5550 of Federal Specifications CCC-T-19 LB exhibit a progressive shrinking of about 7.2% in the warp direction and about 2.4% in the filling direction. When the fabric samples are subjected to the Sanforizing treatment, the progressive shrinkage after the tenth wash is somewhat higher than that of the corresponding cotton fabrics, being about 2.6% in both the Warp and filling directions.

The warp tensile strength of the fabrics in a conditioned state was about 84 pounds as compared to a tensile strength of 63 pounds for a corresponding cotton fabric. The fabric tensile strengths were measured by the conventional grab test method on a Scott DH Tester. -In the wet condition, fabrics formed in accordance with the present invention showed a Warp tensile strength of about 70 pounds as compared to a tensile strength of 72 pounds for the corresponding cotton fabric.

In comparing the warp tensile strength of the fabrics of this invention and corresponding cotton fabrics subjected to the 5% resin finish, the fabrics of the present invention in a conditioned state showed a tensile strength of 8.1 pounds as compared to a tensile strength of 35 pounds for the corresponding cotton fabric. -In the wet state, the fabrics of this invention showed a '63 pound tensile strength as compared to a 37 pound tensile strength in the case of the cotton fabrics.

Tear strengths were measured using the Elmendorf Tear Test Machine in Method 5132 of Federal Specifications CCC-T 'l9 LB. The plain finish tear strength of the fabrics of this invention was found to be 2.1

pounds as compared to 2.6 pounds for the cotton samples. For the samples subjected to the resin treatment, the tear strength of the fabrics of this invention were 8 pounds as compared to 1.4 pounds for the cotton 8 to 70% by weight of the fabric of regenerated cellulose fibers as defined in claim 1.

4. A method 'of forming regenerated cellulose filaments which comprises extruding viscose containing about fabrics. 5 6% cellulose, about 7% caustic soda, about 34% carbon Although the foregoing example represents the predisulfide, based upon the weight of the cellulose, about ferred viscose and bath compositions and the spinning 3.3% dimethylamine, based upon the weight of the celluconditions, the fibers formed as described are representalose, and about 1.7% of a polyoxyethylene glycol ether tive of fibers formed Within the ranges set forth hereinof phenol, based upon the weight of the cellulose, containabove. This is demonstrated by the data in the table 10 ing about ethylene oxide units per mole of phenol and which follows which summarizes compositions and conhaving a sodium chloride salt test of about 8 into a spinditions within the stated ranges. So that there may be a ning bath containing about 7% sulfuric acid, about 11% direct comparison between additional examples and the sodium sulfate and about 4% Zinc sulfate maintained at specific example set forth in detail, the viscose used in a temperature of about 30 C. to form coagulated and forming fibers under various conditions contained 6% 15 partially regenerated cellulose filaments, withdrawing the cellulose, 7% caustic soda and varying proportions of filaments from the spinning bath, passing the filaments carbon disulfide. The various viscoses were aged for through a stretch bath comprising about 3% sulfuric acid, 10 to 30 hours and the sodium chloride salt tests varied about 1.5 zinc sulfate and about 5% sodium sulfate between about 6.5 and 8.3. Two different combinations maintained at a temperature of about 95 C. and stretchof viscose modifiers are represented and like results have ing the filaments in the stretch bath about 140%. been obtained by the use of other modifiers. Samples 5. A method of forming regenerated cellulose fibers designated by the letter A contained 3.3% dimethylamine which comprises extruding viscose containing from about and 1.7% of a polyoxyethylene glycol having a degree of 5% to 7% cellulose, from about 5% to 10% caustic soda, polymerization of about 35 (Carbowax 1540). Samples the ratio of the percentage of cellulose to the percentage designated by the letter B contained 3.3% dimethylamine of caustic soda being from 1:1 to about 1:1.4, from and 1.7% of a polyoxyethylene glycol ether of phenol to 38% carbon disulfide, based upon the weight of the containing an average of 15 ethylene oxide units per mole cellulose, and from about 2% to 5%, based upon the of phenol. In each instance, the proportion of additive weight of the cellulose, of a viscose modifier selected is based upon the weight of the cellulose. from the group consisting of polyoxyalkylene glycols,

It will be noted that the composition of the spinning 30 block copolymers of propylene and ethylene oxides, monobath varied and the temperature of the spinning bath was amines, diamines, polyamines, reaction products of alkylvaried within the ranges set forth hercinabove. The secene oxides with fatty acids, fatty amines, aromatic acids, 0nd or stretch bath had approximately the same composiaromatic alcohols, aromatic amines, partial esters of fatty tion as that set forth in the detailed example. The samacids and polyhydric alcohols, quaternary ammonium ples designated by the letter A were spun at a speed of 27 compounds and mixtures thereof, into a spinning bath meters per minute and the samples designated by the containing 6% to 9% sulfuric acid, 2.5% to 7% zinc letter B were spun at 25 meters per minute. sulfate and from 10% to 14% sodium sulfate maintained The tenacity in the wet state is set forth in grams per at a temperature between 25 C. and C. to form denier and the elongation is reported in percentage in the coagulated and partially regenerated cellulose filaments, wet state. The wet stiffness is represented by the wet 40 withdrawing the filaments from the spinning bath, passstrength divided by the elongation. ing the filaments through an aqueous stretch bath main- Table II Spin Bath Fiber Properties Viscose Percent Temp. Percent, Wet Percent. I'IzSO4 0. Stretch Denier Stifiness Percent Percent T g/d Ew Mw ZnSOl NagSO4 Percent While preferred embodiments of the invention have tained at a temperature between C. and C. and been shown and described, it is to be understood that stretching the filaments in the stretch bath from about changes and variations may be made without departing to about from the spirit and scope of the invention as defined in 6. A method as defined in claim 5 wherein the viscose the appended claims. 65 contains from about 1.5% to 3.5% dimethylamine and We claim: from about 1% to 3% of a polyoxyalklene glycol hav- 1. A regenerated cellulose fiber having a wet tenacity ing a molecular weight of between about 600 and about of at least 3 grams per denier, a conditioned tenacity of 6000, the proportions being based upon the weight of the at least 4.7 grams per denier, a wet modulus of between cellulose in the viscose, the viscose at the time of exabout 12 and 20, a wet extensibility of between about 70. trusion has a sodium chloride salt test of between 7 and 15% and 22% and being further characterized in being 9 and the stretch bath contains from 1% to 5% sulfuric :non-fibrillatable. acid, from 1% to 4% zinc sulfate and from 4% to 7% 2. A fabric formed of regenerated cellulose fibers as sodium sulfate. defined in claim 1. 7. A method as defined in claim 5 wherein the viscose 3. A fabric consisting essentially of cotton and from 75 contains from about 1.5% to 3.5% dimethylamine and from about 1% to 3% of a polyoxyalkylene glycol ether of phenol having a molecular weight of between about 600 and about 6000, the proportions being based upon the weight of the cellulose in the viscose, the viscose at the time of extrusion has a sodium chloride salt test of between 7 and 9 and the stretch bath contains from 1% to 5% sulfuric acid, from 1% to 4% zinc sulfate and from 4% to 7% sodium sulfate.

References Cited by the Examiner UNITED STATES PATENTS 5/1962 Dean et a1 106-165 6/1962 Daimler et al 18-54 7/1962 Burroughs et a1 264-193 10/ 1962 Riley 28-82 11/ 1962 Lytton 264-193 3/1963 Saxton et a1 264-188 10/1963 Kusunose et a1 264-197 11/ 1963 Braunlich et a1 264-193 FOREIGN PATENTS 2/ 1959 Great Britain. 1/1963 Great Britain.

ALEXANDER H. BRODMERKEL, Primary Examiner.

l5 DONALD W. PARKER, Examiner.

A. J. SMEDEROVAC, K. W. VERNON, A. L. LEAV- ITT, J. H. WOO, Assistant Examiners. 

1. A REGENERATED CELLULOSE FIBER HAVING A WET TENACITY OF AT LEAST 3 GRAMS PER DENIER, A CONDITIONED TENACITY OF AT LEAST 4.7 GRAMS PER DENIER, A WET MODULUS OF BETWEEN ABOUT 12 AND 20, A WET EXTENSIBILITY OF BETWEEN ABOUT 15% AND 22% AND BEING FURTHER CHARACTERIZED IN BEING NON-FIBRILLATABLE.
 5. A METHOD OF FORMING REGENERATED CELLULOSE FIBERS WHICH COMPRISES EXTRUDING VISCOSE CONTAINING FROM ABOUT 5% TO 7% CELLULOSE, FROM ABOUT 5% TO 10% CAUSTIC SODA, THE RATIO OF THE PERCENTAGE OF CELLULOSE TO THE PERCENTAGE OF CAUSTIC SODA BEING FROM 1:1 TO ABOUT 1:4, FROM 30% TO 38% CARBON DISULFIDE, BASED UPON THE WEIGHT OF THE CELLULOSE, AND FROM ABOUT 2% TO 5%, BASED UPON THE WEIGHT OF THE CELLULOSE, OF A VISCOSE MODIFIER SELECTED FROM THE GTOUP CONSISTING OF POLYOXYLENE GLYCOLS, BLOCK COPOLYMERS OF PROPYLENE AND ETHYLENE OXIDES, MONOAMINES, DIAMINES, POLYAMINES, REACTION PRODUCTS OF ALKYLENE OXIDES WITH FATTY ACIDS, FATTY AMINES, AROMATIC ACIDS, AROMATIC ALCOHOLS, AROMATIC AMINES, PARTIAL ESTERS OF FATTY ACIDS AND POLYHYDRIC ALCOHOLS, QUATERNARY AMMONIUM COMPOUNDS AND MIXTURES THEREOF, INTO A SPINING BATH CONTAINING 6% TO 9% SULFURIC ACID, 2.5% TO 7% ZINC SULFATE AND FROM 10% TO 14% SODIUM SULFATE MAINTAINED AT A TEMPERATURE BETWEEN 25*C. AND 40*C. TO FORM COAGULATED AND PARTIALLY REGENERATED CELLULOSE FILAMENTS. WITHDRAWING THE FILAMENTS FROM THE SPINNING BATH, PASSING THE FILAMENTS THROUGH AN AAQUEOUS STRETCH BATH MMAINTAINED AT A TEMPERATURE BETWEEN 85*C. AND 100*C. AND STRETCHING THE FILAMENTS IN THE STRETCH BATH FORM ABOUT 125% TO ABOUT 160%. 